In an industrial application such as a manufacturing assembly line or general material handling situation, the payload may be too large for a human operator to move without mechanical assistance or risking injury. Even with lighter loads it may be desirable to provide a human operator with mechanical assistance in order to allow more rapid movement and assembly, avoid strain, fatigue or repetitive motion injuries. Thus, a great deal of industrial assembly and material handling work is done with the help of assist devices such as x-y overhead rail systems. There are two primary examples of these types of devices: (1) powered overhead gantry cranes for large loads, usually running on I-beams, and (2) unpowered overhead rail systems for smaller loads running on low-friction enclosed rails.
These types of assist devices may be passive devices or active devices. For smaller loads, a passive overhead rail system may be used to assist an operator in supporting the load. The operator may push on the payload directly, causing the trolley and bridge rail to move along with the payload to assist the operator in handling the load.
A number of problems, however, plague unpowered overhead rail systems. Getting the payload moving is not the primary one. This can be done by forward pushing, using the large muscles of the lower body which are not easily injured. Controlling the motion of the moving payload is a greater problem, as it requires pulling sideways with respect to the payload's direction of motion, generally using the smaller and more easily injured muscles of the upper body and back.
Anisotropy is a further problem. Although low-friction designs are used, both the friction and the inertia are greater in the direction in which the payload has to carry with it the whole bridge rail than in the direction in which the payload simply moves along the bridge rail. Anisotropy produces an unintuitive response of the payload to applied user forces and often results in the user experiencing a continuous sideways “tugging” as the payload moves, in order to keep it on track. Both steering and anisotropy contribute to ergonomic strain, lower productivity, and a changeover to slower gantry cranes at an unnecessarily low payload weight threshold.
Active devices can be used to generate additional forces which an operator can call upon to further assist in supporting or moving a payload. For larger loads, an active motor-driven trolley and bridge rail transport can be used to assist the operator by providing a mechanical assist. Such additional forces can be generated by motors, balancers, hydraulics, etcetera, which can typically be controlled by the operator.
Intelligent Assist Devices (“IADs”) are a class of computer-controlled machines that interact with a human operator to assist in moving a payload. IADs may provide a human operator a variety of types of assistance, including supporting payload weight, helping to overcome friction or other resistive forces, helping to guide and direct the payload motion, or moving the payload without human guidance. The Robotics Industries Association T15 Committee on Safety Standards for Intelligent Assist Devices describes IADs as a single or multiple axis device that employs a hybrid programmable computer-human control system to provide human strength amplification, guiding surfaces, or both. These multifunctional assist devices are designed for material handling, process and assembly tasks that in normal operation involve a human presence in its workspace. Typically, Intelligent Assist Devices (IADs) are force-based control devices that range from single axis payload balancing to multiple degree of freedom articulated manipulators.
IADs may have multiple modes of operation such as a hands-on-controls mode providing a powered motion of the IAD when the human operator is in physical control and contact with the IAD primary controls. In addition, a hands-on-payload mode provides a selectable powered motion of the IAD in response to the operator positively applying forces to the payload or tooling, when the operator's hand(s) are not on the primary controls. A hands-off mode provides a powered motion of the IAD that is not in response and proportion to forces applied by the operator. Within each of these modes, the IAD may employ features such as force amplification, virtual guiding surfaces, and line tracking technologies.
Because IADs are intended for close interaction with human operators, unambiguous communication of IAD mode of operation to the human operator is particularly important. The man-machine interface should be clearly and ergonomically designed for efficient use of the system and safety of the operator. Ease and intuitiveness of operation is necessary for achieving high levels of productivity. Because of the close interaction of man and machines, safety of the human operator is most important. For example, the IAD mode shall be signaled by a continuous mode indicator that is readily visible to the operator and to other personnel in or near the IAD's workspace. Furthermore, attention should be paid to the design of the operator's controls such that inadvertent or mistaken changes of mode are minimized.
Another main objective in developing IADs is to merge the best of passive and active devices. Needed is the powered assistance currently available with gantry cranes, but the quick and intuitive operator interface that currently is available only from unpowered rail systems is also desirable. Needed is better ergonomic performance than unpowered rail systems and greater dexterity and speed than gantry cranes allow. Also needed is the ability to use the IAD with larger payloads than current unpowered rail systems allow.
In addition, needed is the ability to connect and integrate a number of IAD components to work together, and a computer interface design that allows an technician or system integrator to easily program, operate and monitor the status of an IAD system made up of a plurality of components.